1. Field of the Invention
The present invention relates to a microwave probe having a thermal insulating structure and a detecting apparatus to detect breakage of a rotarybody in an atmospher of high temperature using the probe.
2. Description of the Prior Art
In recent years, microwave circuits can be constituted using a quite compact IC structure by development of a solid state circuit element, a microstrip and the like. With this devlopement, application of microwave has been tried in various measuring fields other than communication. In U.S. Pat. No. 4,384,480 for example, method and apparatus are disclosed where microwave is transmitted into a combustion chamber of an engine and top dead center position of a piston is determined from the received waveform.
For such purpose, a microwave probe must be installed on a wall of a combustion chamber rising to a high temperature beyond 1000.degree. C. In a probe structure of the prior art, the heat from this combustion chamber may be conducted to a coaxial cable or a circuit device connected to the probe, and therefore the deterioration of such connected device is apt to occur. On the other hand, in order to detect breakage of a rotary body rotating at high speed in an atmosphere of high temperature, such as a turbine, an apparatus to detect abnormal vibration or abnormal sound in a rotary shaft has been proposed in the prior art. In this apparatus, however, the broken portion cannot be specified securely and reliability of the detection is not very high.